The present invention relates generally to compression-type fittings such as for coupling the end of a length of tubing to another member, and more particularly to such a fitting which is of an anti-rotation type and which may used as a replacement for conventional lock or safety wire fittings.
Compression fittings are widely used in a variety of instrumentation, pneumatic, hydraulic, process, power, refrigeration, industrial, mobile, transportation, aerospace, military, and other fluid power or control applications utilizing plastic or metal tubing. Typically employing an internally or externally threaded nut and an associated ferrule, flare, or other tube end which is formed or provided to seal between the tubing and a complementary-threaded, relative to the nut, nipple, adapter, body, or other connector, these fittings have been adapted for use with many different tubing types including metals such as copper, brass, steel, stainless steel, titanium, aluminum, and alloys such as nickel-copper, Hastelloy®, Alloy 600, 6Mo, Inconel®, Incoloy®, and the like, and many plastics.
Particularly for commercial or military aerospace applications, it may be specified, such as in accordance with Aerospace Standard AS1043 and Military Standard MS33540, that the fitting connection be safety or “lock” wired after assembly to prevent the accidental loosening of the fitting due to vibration or other forces which may be developed in the service environment. Representative lock wire fittings are shown, for example, in U.S. Pat. Nos. 3,807,774; 2,642,108; and 2,051,899.
In practice, the safety wiring of the connection can be difficult. Accordingly, special fittings have been designed which eliminate the need for safety wiring. Generally, these fittings employ a modified adapter having a collar or other arrangement of tangs which engage a series of grooves provided on the nut (or vice versa) so as to provide a ratcheting effect which in service delimits the rotation of the nut relative to the adapter, but which still allows for the connection to be disassembled using a wrench or other tool. Representative fittings of this type are shown, for example, in U.S. Pat. Nos. 6,309,154; 6,302,447; 6,293,595; 5,823,702; 5,586,790; 5,388,866; 5,362,110; 5,083,819; 5,058,930; and 2,731,058.
It is believed, however, that further improvements in the design of “lockwireless” fittings, i.e., anti-rotation fittings which do not employ a lock wire, would be well-received for commercial and military aerospace use, as well as for other applications. In this regard, the fittings which heretofore have constituted the state of the art typically must employ specially designed adapters and other components which may involve added expense, require special tools or steps for make-up, and/or may not be as robust as conventional componentry if dropped or otherwise subjected to rough handling. Accordingly, it is believed that particularly desired would be a “lockwireless” fitting which employs more standard componentry, which is robust, and which may be made or disassembled in a more conventional fashion so as to have a familiarity to technicians and other involved in the installation or maintenance thereof.